Many types of hardware are available both for the fixation of bones that are fractured and for the fixation of bones that are to be fused (arthrodesed).
For example, the human pelvic girdle (see FIGS. 1 and 2) is made up of three large bones joined together by three relatively immobile joints. One of the bones is called the sacrum and it lies at the bottom of the lumbar spine, where it connects with the L5 vertebra. The other two bones are commonly called “pelvic bones” and are technically referred to as the right ilium and—the left ilium. The sacrum connects with both pelvic bones at the sacroiliac joint (in shorthand, the SI-Joint).
The SI-Joint functions to transfer forces from the spine to the lower extremities, and vice-versa. The SI-Joint has been identified as the pain generator in up to 22% of patients who present with lower back pain.
Sacroiliac joint fusion is a surgical procedure that is performed to alleviate pain coming from the SI joint in patients who have failed to receive adequate pain relief with non-surgical treatments of the SI joint. Some conditions of the SI joint that may be treated with SI joint fusion (arthrodesis) are: degenerative sacroiliitis, inflammatory sacroiliitis, iatrogenic instability of the sacroiliac joint, osteitis condensans ilii, or traumatic fracture dislocation of the pelvis. Currently, screws and screws with plates are used as the standard instrumentation for sacro-iliac fusion. Historically, an SI joint fusion consisted of an open surgical approach to the SI joint from an anterior, a posterior, or a lateral direction. The surgeon would then debride (remove) the cartilage from the articular portion of the joint and the interosseous ligament from the fibrous portion of the joint. These open approaches require a large incision and deep soft tissue dissection to approach the damaged, subluxed, dislocated, fractured, or degenerative SI joint.
A typical technique for placing implants involves placement of one or multiple implants from a lateral to medial direction across the SI-Joint. These implants are placed with a starting point on the lateral aspect of the ilium. The implants are then directed across the ilium, across the sacroiliac joint and into the sacrum. Regarding implant position, care is taken to avoid impinging on neural and vascular structures, including neural tissue within the neural foraminae or spinal canal. In addition, care must be taken to place the implants across the SI joint and avoid the leading tip(s) of the implant(s) violating the osseous envelope of the sacrum. However, the density of the bone in different portions of the sacrum is not typically a consideration during implant placement.
Accordingly, it would be desirable to provide systems and methods for placing multiple implants across the SI-Joint into those portions of the sacrum with relatively higher bone density. Implants placed into denser (stronger) bone will demonstrate improved short-term and long-term mechanical stability of the implant construct spanning the SI-Joint post implantation.